The latest release of JBIG-KIT can be downloaded from

http://www.cl.cam.ac.uk/~mgk25/jbigkit/

JBIG-KIT implements JBIG1, a highly effective data compression
algorithm for bi-level high-resolution images such as fax pages
or scanned documents.

JBIG-KIT provides two variants of a portable library of compression
and decompression functions with a documented interface. You can very
easily include into your image or document processing software. In
addition, JBIG-KIT provides ready-to-use compression and decompression
programs with a simple command line interface (similar to the
converters found in Jef Poskanzer's PBM graphics file conversion
package).

Major new feature in version 2.0:

light-weight, low-memory, streaming T.85-profile implementation

The JBIG-KIT 1.x implementation was designed to be feature-rich. It
implemented most facilities of the standard, in particular progressive
coding (multiple resolution layers). To offer this flexibility...